A conventional circulating water system for aquaculture is disclosed in TW Filing No. 101496697 and contains: at least one aquaculture tank, an aeration unit, a sterilization unit, at least one water circulating tank, a plurality of membrane filtering units, a water returning unit, and a spraying unit. The aeration unit aerates airs to aquaculture water in aquaculture tank, such that the aquaculture tank is full of dissolved oxygen, and baits and excrements overflow out of the aquaculture tank, thereafter the sterilization unit supplies ozone, and an antibacterial layer is mounted in the aquaculture tank to prevent breeding viruses and bacteria, thus increasing aquaculture density and survival rate.
However, fishes secret and discharge mucus, and the mucus attaches with the baits and the excrements having protein and a part thereof is discharged out of the aquaculture tank and is decomposed to ammonia, thereafter the ammonia is eliminated by nitrosomonas after nitrification. But most part of the mucus is pumped toward a filtering room of each membrane filtering unit and attaches on a filtration film to block an opening of the filtration film, thus producing circulating water decreasingly. Even though the spraying unit cleans the filtration film, the mucus cannot be removed from the filtration film easily.
In addition, the baits, the excrements and solid substances cannot overflow the aquaculture tank completely, so bubbles flow on the aquaculture water to form an organic waste layer, and then the organic waste layer is decomposed to the ammonia in the aquaculture tank. The filtration film is an ultra-filtration (UF) film, but the UF film cannot filter the ammonia effectively, in other words, the aquaculture tank remains the ammonia at high density, thereby decreasing the survival rate.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages.